- remove redundant autocmd list
This "grouped" list is useless, it only gets in the way when searching
for event names.
- intro.txt: cleanup
- starting.txt: update, revisit
- doc: `:help bisect`
- mbyte.txt: update aliases 1656367b90. closes#11960
- options: remove 'guifontset'. Why:
- It is complicated and is used by almost no one.
- It is unlikely to be implemented by Nvim GUIs (complicated to parse,
specific to Xorg...).